I thought I would try some of the Java script examples in the sandpit.
The script I tried here checker script tutorial

the instructions state:- Upon load, the script should run, producing a 20 meter x 20 meter
checkered Entity floor under your avatar. After creating the floor, the
script will close itself and vanish from the list of running scripts.

However this is not the case. The script still runs even after I click the stop all scripts button.
It even runs after I have deleted the folder with the script.
So if you go to the SandBox they will be a large white and blue checkerd pattern over the floor.

That script was originally written for Voxels, thats how old it is, and converted to entities this year.
It is designed to be a work platform, it states that, you have to delete them manually.
The script does self close but the floor is persistent.

The entity edit tools were very different then and it was easy to delete a bunch of stuff, now the tools only allow for deleting a single entity at a time.

Here is a script that will clean up all objects around you, delete the floor in one go.Warning, dont run this script anywhere near anything you dont want deleted, you have been warned.

I the only time I ever used voxels was with Cloud Party. But someone in the Cloud Party crew had built it into the game software. I think HIFI is waiting for someone that knows how to develop the feature.